diff options
author | 2016-06-20 08:09:52 -0700 | |
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committer | 2016-06-20 08:09:52 -0700 | |
commit | a4d2d0c798a182d5cc57ce630d31614173f2d67b (patch) | |
tree | a1f0f4e324f8bc65ced4e7b49af3af266f6ad900 /src/core/lib/transport/metadata.c | |
parent | ccc8ec54b0cf75f52c0a19a2674d6a6bc8e93743 (diff) | |
parent | 4e29480e430b94392105934750adfd85cb7849ce (diff) |
Merge github.com:grpc/grpc into reuse_port
Diffstat (limited to 'src/core/lib/transport/metadata.c')
-rw-r--r-- | src/core/lib/transport/metadata.c | 43 |
1 files changed, 21 insertions, 22 deletions
diff --git a/src/core/lib/transport/metadata.c b/src/core/lib/transport/metadata.c index 82c8e239f6..0677f29766 100644 --- a/src/core/lib/transport/metadata.c +++ b/src/core/lib/transport/metadata.c @@ -129,7 +129,10 @@ typedef struct mdtab_shard { internal_metadata **elems; size_t count; size_t capacity; - size_t free; + /** Estimate of the number of unreferenced mdelems in the hash table. + This will eventually converge to the exact number, but it's instantaneous + accuracy is not guaranteed */ + gpr_atm free_estimate; } mdtab_shard; #define LOG2_STRTAB_SHARD_COUNT 5 @@ -217,7 +220,7 @@ void grpc_mdctx_global_init(void) { mdtab_shard *shard = &g_mdtab_shard[i]; gpr_mu_init(&shard->mu); shard->count = 0; - shard->free = 0; + gpr_atm_no_barrier_store(&shard->free_estimate, 0); shard->capacity = INITIAL_MDTAB_CAPACITY; shard->elems = gpr_malloc(sizeof(*shard->elems) * shard->capacity); memset(shard->elems, 0, sizeof(*shard->elems) * shard->capacity); @@ -232,7 +235,7 @@ void grpc_mdctx_global_shutdown(void) { gc_mdtab(shard); /* TODO(ctiller): GPR_ASSERT(shard->count == 0); */ if (shard->count != 0) { - gpr_log(GPR_DEBUG, "WARNING: %d metadata elements were leaked", + gpr_log(GPR_DEBUG, "WARNING: %" PRIuPTR " metadata elements were leaked", shard->count); if (grpc_iomgr_abort_on_leaks()) { abort(); @@ -245,7 +248,7 @@ void grpc_mdctx_global_shutdown(void) { gpr_mu_destroy(&shard->mu); /* TODO(ctiller): GPR_ASSERT(shard->count == 0); */ if (shard->count != 0) { - gpr_log(GPR_DEBUG, "WARNING: %d metadata strings were leaked", + gpr_log(GPR_DEBUG, "WARNING: %" PRIuPTR " metadata strings were leaked", shard->count); for (size_t j = 0; j < shard->capacity; j++) { for (internal_string *s = shard->strs[j]; s; s = s->bucket_next) { @@ -281,10 +284,8 @@ static void ref_md_locked(mdtab_shard *shard, grpc_mdstr_as_c_string((grpc_mdstr *)md->key), grpc_mdstr_as_c_string((grpc_mdstr *)md->value)); #endif - if (0 == gpr_atm_no_barrier_fetch_add(&md->refcnt, 2)) { - shard->free--; - } else { - GPR_ASSERT(1 != gpr_atm_no_barrier_fetch_add(&md->refcnt, -1)); + if (0 == gpr_atm_no_barrier_fetch_add(&md->refcnt, 1)) { + gpr_atm_no_barrier_fetch_add(&shard->free_estimate, -1); } } @@ -447,6 +448,7 @@ static void gc_mdtab(mdtab_shard *shard) { size_t i; internal_metadata **prev_next; internal_metadata *md, *next; + gpr_atm num_freed = 0; GPR_TIMER_BEGIN("gc_mdtab", 0); for (i = 0; i < shard->capacity; i++) { @@ -463,13 +465,14 @@ static void gc_mdtab(mdtab_shard *shard) { } gpr_free(md); *prev_next = next; - shard->free--; + num_freed++; shard->count--; } else { prev_next = &md->bucket_next; } } } + gpr_atm_no_barrier_fetch_add(&shard->free_estimate, -num_freed); GPR_TIMER_END("gc_mdtab", 0); } @@ -504,7 +507,8 @@ static void grow_mdtab(mdtab_shard *shard) { } static void rehash_mdtab(mdtab_shard *shard) { - if (shard->free > shard->capacity / 4) { + if (gpr_atm_no_barrier_load(&shard->free_estimate) > + (gpr_atm)(shard->capacity / 4)) { gc_mdtab(shard); } else { grow_mdtab(shard); @@ -553,7 +557,7 @@ grpc_mdelem *grpc_mdelem_from_metadata_strings(grpc_mdstr *mkey, /* not found: create a new pair */ md = gpr_malloc(sizeof(internal_metadata)); - gpr_atm_rel_store(&md->refcnt, 2); + gpr_atm_rel_store(&md->refcnt, 1); md->key = key; md->value = value; md->user_data = 0; @@ -645,7 +649,7 @@ grpc_mdelem *grpc_mdelem_ref(grpc_mdelem *gmd DEBUG_ARGS) { this function - meaning that no adjustment to mdtab_free is necessary, simplifying the logic here to be just an atomic increment */ /* use C assert to have this removed in opt builds */ - assert(gpr_atm_no_barrier_load(&md->refcnt) >= 2); + assert(gpr_atm_no_barrier_load(&md->refcnt) >= 1); gpr_atm_no_barrier_fetch_add(&md->refcnt, 1); return gmd; } @@ -662,18 +666,13 @@ void grpc_mdelem_unref(grpc_mdelem *gmd DEBUG_ARGS) { grpc_mdstr_as_c_string((grpc_mdstr *)md->key), grpc_mdstr_as_c_string((grpc_mdstr *)md->value)); #endif - if (2 == gpr_atm_full_fetch_add(&md->refcnt, -1)) { - uint32_t hash = GRPC_MDSTR_KV_HASH(md->key->hash, md->value->hash); + uint32_t hash = GRPC_MDSTR_KV_HASH(md->key->hash, md->value->hash); + if (1 == gpr_atm_full_fetch_add(&md->refcnt, -1)) { + /* once the refcount hits zero, some other thread can come along and + free md at any time: it's unsafe from this point on to access it */ mdtab_shard *shard = &g_mdtab_shard[SHARD_IDX(hash, LOG2_MDTAB_SHARD_COUNT)]; - GPR_TIMER_BEGIN("grpc_mdelem_unref.to_zero", 0); - gpr_mu_lock(&shard->mu); - if (1 == gpr_atm_no_barrier_load(&md->refcnt)) { - shard->free++; - gpr_atm_no_barrier_store(&md->refcnt, 0); - } - gpr_mu_unlock(&shard->mu); - GPR_TIMER_END("grpc_mdelem_unref.to_zero", 0); + gpr_atm_no_barrier_fetch_add(&shard->free_estimate, 1); } } |